Why do galaxy clusters contain hot X-ray gas?
Quick Answer
As galaxies fall into a cluster’s deep gravity well, gas is heated to tens of millions of degrees. That superheated gas glows strongly in X-rays.
The Full Story
Galaxy clusters are the largest gravitationally bound structures in the universe. When gas and smaller galaxies fall into a cluster, the infalling material collides and gets heated by shocks and compression. The intracluster medium can reach temperatures of tens of millions of kelvin, hot enough to emit X-rays rather than visible light. Much of the normal matter in a cluster is actually in this diffuse hot gas, not in the galaxies themselves. X-ray telescopes such as Chandra and XMM-Newton study this material in detail.
Key Facts
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"Why do galaxy clusters glow in invisible X-rays?"
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